JP6443634B2 - Foaming hot melt adhesive composition and use thereof - Google Patents

Description

  The present invention relates to foamable hot melt adhesive compositions and methods for assembling and sealing boxes, trays, cartons.

  The hot melt adhesive is applied to the substrate in a molten state and cooled to cure the adhesive layer. Such adhesives are widely used in various commercial and industrial applications, such as sealing cardboard boxes, bags, trays and cartons, and bonding laminates of nonwoven and foil articles. In some packaging applications, an adhesive is required to maintain a strong bond to the substrate under excessive stress and impact during handling. In addition, boxes and cartons are often exposed to very high temperatures during transport, and these applications require adhesives with sufficiently good heat resistance. “Sufficiently good heat resistance” means that the bonded adhesive maintains fiber tear at high temperatures, for example above 52 ° C. (125 ° F.), and therefore softens instantly when subjected to high temperature effects It should be understood that this means that the adhesive bond must not be weakened and / or the joints must not deviate from each other.

  Various polymer-based foam hot melt adhesives are described in US 5,342,858, US 5,369,136, US 6,008,262 and JP H-17730. Foamed adhesives include closed cell foams with gas or air pockets in the adhesive matrix. There are various economic and environmental benefits to using foam adhesives, such as lower usage, lower costs, less waste, less storage requirements, and greater gap filling capacity. While the benefits of foamed adhesives are numerous, foamed adhesives are typically less adhesive and less reliable than non-foamed adhesives.

  The present invention seeks to improve the reliability and adhesion of foamed hot melt adhesives. In addition, foamable hot melt adhesives and packages made therefrom provide a more environmentally and economically sound product.

  The present invention relates to a foamable hot melt adhesive composition, a method of foaming a foamable hot melt adhesive composition, and a method of using a foamed hot melt adhesive composition. Foamed hot melt adhesives have high heat resistance and allow reliable bonding for packaging applications. The present invention provides an environmentally and economically sound adhesive that provides sufficient adhesion to the package upon application.

  In one embodiment of the present invention, foamability comprising about 90 to about 99.9 wt% hot melt adhesive and about 0.1 to about 10 wt% of a block copolymer containing alternating blocks of rigid and elastic segments A hot melt adhesive composition is provided. The foamable hot melt adhesive composition optionally includes from about 0.05 to about 10 wt% foam cell former. Upon foaming, the foamed adhesive has a volume percent of about 20 to about 80 V / V%.

  Another embodiment is a foamable hot melt comprising from about 90 to about 99.9 wt% hot melt adhesive and from about 0.1 to about 10 wt% of a block copolymer containing alternating blocks of rigid and elastic segments. Preparing an adhesive composition; heating the foamable hot melt adhesive to a molten state; mechanically mixing gas or air into the molten foamable hot melt adhesive composition; Releasing the hot melt adhesive. A method of foaming the foamable hot melt adhesive is provided.

  Yet another embodiment is a foaming hot comprising about 90 to about 99.9 wt% hot melt adhesive and about 0.1 to about 10 wt% of a block copolymer containing alternating blocks of rigid and elastic segments. Preparing a melt adhesive composition; adding from about 0.05 to about 10 wt% of a foam cell former in the adhesive until a uniform mixture is formed; and a foamable adhesive in hot melt A method of foaming a foamable hot melt adhesive comprising heating the composition to a temperature (T1) and then pumping the adhesive into a hose and / or nozzle having a temperature of T2. provide. T2 is higher than T1, the adhesive is not substantially foamed at T1, and the adhesive reaches a foam at or near maximum at T2. Thus, the foam occurs just before applying the adhesive to the substrate.

  Yet another embodiment of the present invention provides about 90 to about 99.9 wt% of a hot melt adhesive, about 0.1 to about 10 wt% of a block copolymer containing alternating blocks of rigid and elastic segments, and Preparing a foamable hot melt adhesive composition comprising from about 0.1 to about 10 wt% foamed cell forming agent, heating the foamable hot melt adhesive to a molten state, and foaming hot melt adhesion Applying the agent to a substrate of a carton, bag, box or sealer. A method of preparing a carton, bag, box or sealer package is provided.

FIG. 1 is an ARES curve of the modulus with respect to temperature. FIG. 2 is an ARES time sweep curve of tan δ against time. FIG. 3 is a plot of the ratio of foam height against elapsed time.

  All documents cited herein are incorporated by reference in their entirety.

  Weight percent (wt%) is based on the total weight of the adhesive prior to any foaming, unless otherwise noted.

  The term “polymer” is used herein to refer to a homopolymer or a blend of different (co) polymers.

  The present invention has reliable adhesion and improved heat resistance by adding 0.1 to 10 wt% block copolymer containing alternating blocks of rigid and elastic segments into the hot melt adhesive. It is based on the discovery that foamable hot melt adhesives can be obtained. The foamable adhesive compositions described herein may be useful in conventional packaging products such as bags, boxes, cartons or sealers. Foamable adhesive compositions are easily used in conventional equipment with little change in the manufacturing process. Through the use of the foamable adhesive composition of the present invention, a packaged product can be produced with less adhesive and less waste. The end result is an environmentally and economically sound adhesive and packaging product.

  In one embodiment, the present invention provides a block copolymer containing about 90 to about 99.9 wt% hot melt adhesive, about 0.1 to about 10 wt% alternating blocks of rigid and elastic segments, and optionally A foamable hot melt adhesive composition comprising from about 0.05 to about 10 wt% of a foamed cell forming agent. Upon foaming, the foamed adhesive has a volume percent of about 20 to about 80 V / V%, preferably about 30 to about 70 V / V%.

  The hot melt adhesive may be made from any number of materials. Desirably, the hot melt adhesive composition comprises a polymer, a tackifier, optionally a wax, a plasticizer, an oil, a stabilizer, and an additive. The type of hot melt adhesive depends on the end use application and the desired performance characteristics. A typical hot melt adhesive useful in the foamable hot melt adhesive of the present invention is a thermoplastic polymer, although thermosetting adhesives are contemplated.

  The thermoplastic hot melt adhesive may be made from any number of polymers. As used herein, polymers include: ethylene-vinyl acetate; ethylene-acrylate; polyolefins; polyamides; polyesters; thermoplastic polyurethanes; reactive polyurethanes; styrene block copolymers; polycaprolactones; And thermoplastic elastomers; and polypyrrole.

  In a preferred embodiment, the hot melt adhesive in the foamable hot melt adhesive includes a polymer selected from ethylene-vinyl acetate copolymer; ethylene-acrylate copolymer and polyolefin.

  The ethylene-vinyl acetate copolymer preferably has a vinyl acetate content of less than 40% and a melt index measured according to ASTM ranges from about 5 to about 2,500 g / 10 minutes.

  The ethylene-acrylate copolymer has an acrylate content of less than 40% and a melt index measured according to ASTM D1238 ranges from about 5 to about 2500 g / 10 minutes. Examples of ethylene-acrylate copolymers include n-butyl ethylene acrylate, ethylene-acrylic acid and ethylene-ethyl acetate.

As polyolefin polymers _include C 2 _{-C 20} copolymers and terpolymers. Depending on the choice of monomer and comonomer, and catalyst in the polymerization, the polyolefin may be substantially amorphous, semi-crystalline or crystalline. Depending on the degree of crystallinity and molecular weight desired, various monomer combinations may be selected as the polymer for the hot melt adhesive. Both metallocene-catalyzed polyolefins with narrow molecular weight distribution and non-metallocene-catalyzed (Ziegler-Natta catalyst) polyolefins may be selected as the base polymer for the adhesive.

Examples of preferred polyolefins have, for example, C ₂ and C ₃ , C ₄ , C ₅ , C ₆ , C ₇ , C ₈ , C ₉ , C ₁₀ , C ₁₁ and / or C ₁₂ at 190 ° C. measured according to ASTM D1238, having a main belt index of about 5 or exceeds et about 2,500 g / 10 min, in the range from about 10% to about 25% of the total crystallinity of a polymer, ethylene -α Examples include olefins. For example, having C ₃ and C ₂ , C ₄ , C ₅ , C ₆ , C ₇ , C ₈ , C ₉ , C ₁₀ , C ₁₁ and / or C ₁₂ , measured at 190 ° C. according to ASTM D1238 has a main belt index of about 5 or exceeds et about 2,500 g / 10 min, propylene copolymers overall crystallinity in the range from about 10% to about 25% of the polymer, in another preferred olefin is there.

  The polymer content in the thermoplastic hot melt adhesive ranges from about 10 to about 70 wt%, preferably from about 20 to about 60 wt%.

  The tackifier is selected based on the polymer of the hot melt adhesive. Tackifier and polymer miscibility is a major factor in selecting specific tackifiers for hot melt adhesive compositions, but less miscible tackifiers in foamable hot melt adhesives May be used. The tackifier component may typically be present from about 20 to about 80 wt%, preferably from about 30 to about 60 wt%, based on the total weight of the adhesive.

  Typical tackifiers have a ring and ball softening point as determined by ASTM method E28 of from about 70 ° C to about 150 ° C, more preferably from about 95 ° C to about 130 ° C.

Useful tackifying resins include any natural and modified rosins such as, for example, gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, resin acid salt, and polymerized rosin. Compatible resins or mixtures thereof; natural and natural, such as glycerol esters of light wood rosin, glycerol esters of hydrogenated rosin, glycerol esters of polymerized rosin, pentaerythritol esters of hydrogenated rosin, and phenol-modified pentaerythritol esters of rosin Glycerol and pentaerythritol esters of modified rosins; copolymers and terpolymers of natural terpenes, including, for example, styrene / terpene and α-methylstyrene / terpene; determined by ASTM method E28-58T A polyterpene resin having a softening point of about 70 to 150 ° C .; a phenol-modified terpene resin and hydrogenated derivatives thereof, including, for example, a resin product formed by condensation of a bicyclic terpene with phenol in an acidic medium; Includes aliphatic petroleum-based hydrocarbon resins having a ring and ball softening point of 70 ° C. to 135 ° C .; aromatic petroleum-based hydrocarbon resins and hydrogenated derivatives thereof; and alicyclic petroleum-based hydrocarbon resins and hydrogenated derivatives thereof May be. Examples of particularly suitable hydrogenated tackifiers include Escorez 5400 from Exxon Mobile Chemicals, Arkon P100 from Arakawa, Regalite S1100 from Eastman Chemical, and the like. Cyclic or acyclic C ₅ resins and aromatic modified acyclic or cyclic resins may also be used. Examples of commercially available rosins and rosin derivatives that can be used to practice the present invention include SYLVALITE RE 110L from ARISONA Chemical, SYLVARES RE 115 and SYLVARES RE 104; Dertocal 140 from DRT; Arakawa Chemical from . 1, GB-120 and Pencel C. Examples of commercially available phenol-modified terpene resins are Sylvares TP 2040 HM and Sylvares TP 300, both available from Arizona Chemical.

  In one embodiment, the tackifier is a synthetic hydrocarbon resin. Aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons, aromatic modified aliphatic or alicyclic hydrocarbons and mixtures thereof are included.

Non-limiting examples include aliphatic olefin-derived resins such as those available from Goodyear under the trade name WINGTACK (R) Extra, and the ESCOREZ (R) 1300 series from Exxon. Common C ₅ tackifying resin in this class has a softening point of about 95 ° C., a diene of piperylene and 2-methyl-2-butene - olefin copolymer. This resin is commercially available under the trade name Wingtack 95. Eastman's Eastotac series is also useful in the present invention.

Be derived from C ₉ aromatic / aliphatic olefin, aromatic hydrocarbon resin from a and Rutgers tradename NorSolene from Sartomer and Cray Valley which is commercially available as TK aromatic hydrocarbon resins series are also useful. Norsolene M1090 is a low molecular weight thermoplastic hydrocarbon polymer having a ring and ball softening point of 95-105 ° C. and is commercially available from Cray Valley.

  Α-methylstyrenes such as Kristalex 3085 and 3100 from Eastman Chemicals and Sylvares SA 100 from Arizona Chemicals are also useful as tackifiers in the present invention. Such an adhesive blended with α-methylstyrene results in a viscosity of less than about 1500 mPa · s at 121 ° C. A mixture of two or more described tackifying resins may be required for some formulations.

  A small amount of an alkylphenol-based tackifier can be blended with the further tackifiers detailed above to improve the high temperature properties of these adhesives. Alkyl phenolic resins added at less than 20 wt% of the total weight of the adhesive are compatible and improve high temperature adhesive properties in the proper combination. Alkylphenol resins are commercially available from Arakawa Chemical under the trade name Tamanol, and are a number of product lines by Scientady International.

  The hot melt adhesive of the present invention may optionally contain waxes, plasticizers, oils, stabilizers, and additives.

  Suitable waxes for use in the present invention include paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, by-product polyethylene wax, Fischer-Tropsch wax, oxidized Fischer-Tropsch wax, and hydroxy stearamide wax and fatty amide. Functionalized waxes such as waxes are included. High density low molecular weight polyethylene waxes, by-product polyethylene waxes and Fischer-Tropsch waxes are commonly referred to in the art as synthetic high melting point waxes.

  Paraffin waxes that can be used in the practice of the present invention include Citgo Petroleum, Co. More available PACEMAKER® 30, 32, 35, 37, 40, 42, 45 and 53; ASTOR OKERIN® 236 available from Honeywell; R-7152 paraffin wax available from Moore &Munger; Moore and other paraffin waxes such as those available under the product names Sasolwax 5603, 6203 and 6805 from Sasol Wax.

  Microcrystalline waxes useful herein are those having 50 weight percent or more of cyclic or branched alkanes having a length of 30 to 100 carbon atoms. These are generally less crystalline than paraffin and polyethylene waxes and have melting points above about 70 ° C. As an example, Baker Petrolite Corp. VICTORY® Amber Wax, a 70 ° C. melting point wax available from Bareco; BARECO® ES-796 Amber Wax, a 70 ° C. melting point wax available from Bareco; all from Baker Petrolite Corp. BESQUARE® 175 and 195 amber waxes, 80 ° C. and 90 ° C. melting point microcrystalline waxes; Indramic® 91, 90 ° C. melting point wax available from Industrial Raw Materials; and PETROWAX® 9508 Light, a 90 ° C. melting point wax available from Petrowax. Other examples of microcrystalline waxes are Sasolwax 3971 available from Sasol Wax and Microwax K4001 available from Alfred Kochem GmBH.

Exemplary high density low molecular weight polyethylene waxes that fall into this category include Backer Petrolite Corp. And ethylene homopolymers available as POLYWAX ™ 500, POLYWAX ™ 1500 and POLYWAX ™ 2000. POLYWAX ™ 2000 has a molecular weight of about 2000, a Mw / Mn of about 1.0, a density of about 0.97 g / cm ³ at 16 ° C., and a melting point of about 126 ° C.

  When used, the wax component will typically be present in an amount up to about 40 wt% with respect to the thermoplastic hot melt adhesive. Formulations containing a wax component will more typically contain up to about 40 wt% wax component. Preferred waxes have a melting temperature between 49 ° C and 121 ° C, more preferably between 66 ° C and 110 ° C, and most preferably between 82 ° C and 104 ° C.

  The adhesive of the present invention may optionally contain a plasticizer such as oil. Suitable plasticizers include polybutene, polyisobutylene, phthalate, benzoate, adipic acid ester and the like. Particularly preferred plasticizers include phthalates such as polybutene and polyisobutylene, di-iso-undecyl phthalate (DIUP), di-iso-nonyl phthalate (DINP), dioctyl phthalate (DOP), mineral oils, aliphatic oils, oligomers of olefins And low molecular weight polymers, vegetable oils, animal oils, paraffinic oils, naphthenic oils, aromatic oils, long chain partial ether esters, alkyl monoesters, epoxidized oils, dialkyl diesters, aromatic diesters, alkyl ether monoesters and mixtures thereof Can be mentioned. In one embodiment, the plasticizer has a number average molecular weight greater than 1000 g / mol. In another embodiment, the plasticizer is typically present at up to about 35 wt%, more preferably up to 30 wt%, based on the total weight of the thermoplastic hot melt adhesive.

  The hot melt adhesive composition of the present invention may desirably further contain at least one stabilizer and / or at least one antioxidant. These compounds are added to protect the adhesive from decomposition due to reaction with oxygen, such as induced by heat, light, or residual catalyst derived from raw materials such as tackifying resins.

  As used herein, applicable stabilizers or antioxidants include high molecular weight hindered phenols and multifunctional phenols such as sulfur-containing and phosphorus-containing phenols. Hindered phenols are well known to those skilled in the art and can be characterized as phenolic compounds that further include sterically bulky groups near their phenolic hydroxyl groups. In particular, tertiary butyl groups generally replace the benzene ring at at least one ortho position relative to the phenolic hydroxyl group. The presence of these sterically bulky substituents in the vicinity of the hydroxyl group serves to suppress its stretching frequency and correspondingly its reactivity. Stabilizing properties are provided. Representative hindered phenols include 1,3,5-trimethyl-2,4,6-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -benzene; pentaerythrityltetrakis-3 ( 3,5-di-tert-butyl-4-hydroxyphenyl) -propionate; n-octadecyl-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4′-methylenebis (2, 6-tert-butyl-phenol); 4,4′-thiobis (6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol; 6- (4-hydroxyphenoxy) -2,4-bis (N-octyl-thio) -1,3,5 triazine; di-n-octylthio) ethyl 3,5-di-tert-butyl-4-hydride Carboxymethyl - benzoate and sorbitol hexa [3- (3,5-di -tert- butyl-4-hydroxy - phenyl) - propionate] and the like.

  Such antioxidants are commercially available from Ciba Specialty Chemicals and include hindered phenols IRGANOX® 565, 1010, 1076 and 1726. These are primary antioxidants that act as radical scavengers, which can be used alone or other oxidants such as phosphite antioxidants such as IRGAFOS® 168 available from Ciba Specialty Chemicals. It may be used in combination with an inhibitor. The phosphite catalyst is considered a secondary catalyst and is generally not used alone. These are mainly used as peroxide decomposers. Other available catalysts are CYANOX® LTDP and Albemarle Corp. available from Cytec Industries. ETHANOX® 330, which is more available. Many such antioxidants are available for use alone or in combination with other such antioxidants. These compounds are added in small amounts in the hot melt, typically less than about 10 wt% with respect to the thermoplastic hot melt adhesive, and do not affect other physical properties. Other compounds that can be added and do not affect the physical properties are pigments that give color, or fluorescent agents, to name just a few. Additives such as these are known to those skilled in the art.

  Depending on the intended end use of the adhesive, other additives such as pigments, dyes and fillers conventionally added to hot melt adhesives may be used in small amounts, ie up to about 10% by weight of the present invention. It may be incorporated into the formulation.

  It has been discovered that the presence of a block copolymer containing alternating blocks of rigid and elastic segments helps to form a stable foam and improves the adhesion and heat resistance of the foam adhesive layer. These block copolymers are high molecular weight, low melt index polymers. It is essential that the block copolymer contains alternating blocks of rigid and elastic segments. Not all polymers with high molecular weight and low melt index are useful in the foamable hot melt adhesives of the present invention, and they do not impart the desired properties to the foamed adhesive.

  In one embodiment, the alternating blocks of rigid and elastic segments are styrene block copolymers, also known as rubber-based resins. The styrene block copolymer may be linear or radial with more than three arms. Examples of the styrene block copolymer include styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene / butylene-styrene, and styrene-ethylene / propylene copolymer.

  In another embodiment, the alternating block component of the rigid and elastic segment component is an olefin block copolymer (OBC) produced by a chain shuttling process. The OBC has “hard” (highly rigid crystalline) segments and “soft” (highly elastic amorphous) segment blocks. US Pat. No. 7,524,911 and WO2009 / 029476 describe adhesive compositions based on OBC. Other references describing OBC and various applications for OBC include WO 2006/101966, WO 2006/102016, WO 2008/005501 and WO 2008/066753.

Preferred OBC polymer components have a density of 0.870 g / cm ³ or higher, a melt index of greater than 5 g / 10 minutes measured at 190 ° C. according to ASTM D1238, and a DSC melting point of greater than 100 ° C. The DSC melting temperature can be measured by various means known in the art. The DSC melting temperature values given herein are measured by a TA Instruments Q200 differential scanning calorimeter. About 5 to 10 mg of sample was sealed in a sealed aluminum pan, nitrogen gas was used as a carrier gas, and measurement was performed using air (empty pan) as a reference. The sample was heated above the melting point of the sample (typically up to 220 ° C.) and kept isotherm for 5 minutes. The sample was then cooled at 10 ° C./min to −50 ° C. and the isotherm was held for an additional 5 minutes to allow crystallization. The sample was heated a second time at a rate of 10 ° C./min. The resulting DSC data was analyzed by the peak program and the peak temperature, onset temperature and melting temperature were determined by the program software. In one embodiment, the OBC comprises a copolymer of ethylene and at least one comonomer selected from C _3-10 α-olefins. In another embodiment, the OBC comprises a copolymer of propylene and at least one comonomer selected from _{C2,4-10 [} alpha] -olefins. In one particular embodiment, the OBC component is an ethylene-octene comonomer. The OBC described above can be purchased from Dow under the trade name INFUSE (registered trademark).

  Preferably, the polymer in the foamable hot melt adhesive has a ratio of hot melt adhesive polymer to alternating block copolymer of from about 20: 1 to about 2: 1. In another embodiment, the ratio of hot melt adhesive polymer to alternating block copolymer is in the range of about 15: 1 to 3: 1.

  Without being bound by any particular theory, the presence of a block polymer improves the adhesion, temperature resistance and cure time of hot melt adhesives, which can be further extended to a foamed state. It is thought that it becomes. This addition also improves the tensile properties of the hot melt adhesive, which enables good adhesion without cohesive failure of the foamed adhesive layer. The closed cell foam is believed to remain in the adhesive matrix and will not aggregate and rise to the surface of the adhesive and collapse. Therefore, a foamed adhesive having a closed cell structure can be applied to the substrate, and this adheres to the substrate. Foamed adhesive has gel-like properties and maintains a high modulus even under compression and high temperatures.

  The foamable adhesive of the present invention is prepared by blending the components of the hot melt adhesive in the range of about 100 ° C. to about 130 ° C. to form a uniform blend. The specific temperature depends on the minimum temperature at which the foaming agent foams and the melting temperature of the hot melt adhesive. Various blending methods are known in the art. The molten blend may then be cooled and formed into pellets, blocks or films for storage or transportation. These preformed adhesives can then be reheated, foamed and applied to the substrate.

  Depending on the equipment, various methods of foaming the foamable hot melt adhesive can be implemented. In general, the foam is formed by first melting or remelting the hot melt adhesive composition into a molten state. A preferred foaming method is performed using gas, foamed cell forming agent or microspheres.

  When foaming with a gas, a suitable gas is used to mix the molten thermoplastic composition under sufficient pressure to form a gaseous solution or dispersion in the molten thermoplastic composition. To form an effervescent mixture or solution. Upon sufficient pressure drop caused by distributing the mixture at atmospheric pressure, a gas is generated from the solution in the form of bubbles in the molten thermoplastic composition and / or the gas spreads into the solution and the adhesive matrix A closed cell structure is formed inside.

  The gas is preferably non-reactive, particularly non-oxidizing, and includes inert gases such as nitrogen, carbon dioxide, argon and helium, and mixtures thereof. Although oxidizing gases such as air are typically not preferred, they may be used for adhesives that are thermally stable and applicable at low temperatures (eg, 130-250 ° C.).

  One suitable method of incorporating gas into the foamable hot melt adhesive utilizes the Foam-Melter 130 system, available from NORDSON®. The foamable hot melt adhesive composition is then released from the solution when the adhesive / gas solution is discharged at atmospheric pressure, and is encapsulated in a thermoplastic material to form a relatively uniform foam. Under such pressure, it may be mechanically mixed with the gas to obtain a molten adhesive / gas solution.

  The thermoplastic adhesive must have sufficient mechanical strength or stiffness to maintain foam stability in the adhesive matrix. Adhesives with a viscosity of less than 500 cP are insufficient to keep the foam in the matrix because the foam collapses, while adhesives with a viscosity greater than 1,000,000 have high pressure. Required.

  In another method, a foam cell forming agent is added to the foamable hot melt adhesive to promote foaming. In the case of foaming performed using a foamed cell forming agent, by raising the temperature to a temperature exceeding the decomposition T2 of the foamed cell forming agent, gas is generated in the foamable hot melt adhesive, and independent in the adhesive matrix. A bubble structure is formed. Typical blowing agents include azobisformamide, semicarbazide, tetrazole, benzoxazine, hydrazine and liquid fluorocarbons. Preferred foaming cell forming agents include azodicarbonamide, oxybis (benzenesulfonyl hydrazide), toluenesulfonyl hydrazide, diphenylsulfone-3,3′-disulfohydrazide, trihydrazinotriazine, p-toluenesulfonyl semicarbazide, 5-phenyltetrazole. , Isatoic anhydride, sodium bicarbonate, citric acid, and derivatives and combinations thereof. A foam is produced | generated by decomposition | disassembly of the foaming cell formation agent under predetermined high temperature. The foam cell former is in the range of about 0.05 to about 10 wt%, preferably about 0.1 to about 8 wt%, more preferably about 0.5 to about 7 wt%, based on the total foamable adhesive. It may be a range.

  Decomposition of the foam cell forming agent releases N 2, CO, NH 3, H 2 O and / or CO 2 gases / vapors that form the foam matrix cells. By subjecting the foamable hot melt adhesive to a temperature equal to or higher than the decomposition temperature of the foamed cell forming agent based on the decomposition temperature of the foamed cell forming agent, gas is released into the adhesive and a foam is produced. The foam has a closed cell structure. Another chamber in which the foamable adhesive was melted at a certain temperature (T1) and the molten adhesive was set to a higher temperature (T2) (T2 is higher than T1) for a more efficient process Or move to nozzle. T2 is typically selected and varies based on the decomposition temperature of the foam cell forming agent. By using pressure, the foamed adhesive is pushed to ambient pressure toward the substrate.

  The selection of T2 depends on the decomposition temperature of the foam cell forming agent and the viscosity of the hot melt at the application temperature. The hose / nozzle T2 must be near or above the decomposition temperature of the foam cell former in order to initiate the foam cell former decomposition and cause the adhesive to foam. However, T2 should not be too high to reduce the viscosity of the adhesive to a level that cannot support the foam in the adhesive matrix (eg, less than 500 cPs).

  In order to change the decomposition temperature of the foam cell forming agent, further additives such as a decomposition initiator may be added in combination with the foam cell forming agent. Examples of the decomposition initiator include zinc oxide, zinc stearate, urea, triethanolamine and the like.

  Pre-expanded and expandable microspheres can also be added to the foamable hot melt adhesive. When the temperature of the adhesive is raised, the foaming agent inside the expandable microsphere is thermally decomposed to expand the microsphere. Depending on the temperature at which pyrolysis occurs, the melting and foaming of the adhesive can be controlled to meet the desired application requirements. In the case of pre-expanded microspheres, these can be added directly to the foaming hot melt adhesive to reduce the density and to have closed cell properties.

  The foamed adhesive contains from about 20 to about 80 V / V%, preferably from about 30% to about 70%, more preferably from about 40% to about 60% foamed gas or air.

  Without being bound to a particular theory, the combination of alternating blocks of rigid and elastic segments and a thermoplastic hot melt adhesive improves the tensile properties of the foamed adhesive and thus reduces the density of the adhesive Even when this is done, the cohesive strength of the adhesive layer is considered to be maintained at a sufficient level. Furthermore, since the foamed adhesive has higher compression and modulus values at high temperatures, it is believed that the closed cell structure of the foamed adhesive behaves like a gel.

  In another embodiment of the present invention, the heat resistance of the foamed hot melt adhesive composition of the present invention is improved over foamed hot melt adhesives that do not have alternating blocks of rigid and elastic segments. The heat resistance of this foamed hot melt adhesive is increased by at least 5 ° C. over foamed hot melt adhesives that do not have a block copolymer with alternating blocks of rigid and elastic segments. The foamed adhesive of the present invention has a heat resistance that is increased by at least 5 ° C., preferably by at least 10 ° C., relative to an adhesive not using a block copolymer. Desirably, the adhesive can be formulated for normal and low temperature applications, ie, a formulation that can be applied at a temperature of about 177 ° C. (350 ° F.) down to about 93 ° C. (200 ° F.). It is. They allow excellent adhesive bonding even when exposed to a wide range of temperature conditions.

  The application of foamable adhesives is known to those skilled in the art. The adhesive of the present invention may be applied to the desired substrate by any method known in the art, including but not limited to a slot die, such as Nordson Foammelt 130.

  The foamed adhesive may be applied to cardboard boxes, bags, books, graphic arts, trays, cartons and sealers. The foamed adhesive may be applied to films, foils and nonwoven materials to form a laminate. The foamed adhesive may be formed as a tape. A foamable adhesive is applied to the film and cooled to a specific viscosity or temperature, but a second film may be placed directly on the foamed adhesive and allowed to cool completely to room temperature to form an adhesive tape. The tape can be tacky and can have pressure sensitive properties. The tape can be wound and stored for transport and future use. Depending on the level of foam in the adhesive, the adhesive has thermal insulation properties, cushioning properties, protective properties and / or pressure sensitive properties.

  Various adhesive samples were prepared using the components shown in Tables 1-5. An adhesive was prepared by combining the components at 130-170 ° C. until a uniform mixture was formed.

  For the above samples, cure time and percent fiber tear were measured at various density reductions and application temperatures. The percent density reduction is shown in Table 2, where 0% represents the absence of foam in the adhesive. Sample density was reduced using mechanical agitation and applicator Nordson Foammelt 130. Using a density cup, the percent reduction was measured by controlling the volume and mass of the adhesive. The nozzle temperature of the foam adhesive applicator is shown below as the application temperature. Beads (weights listed in Table 2) were applied to the entire 5 cm wide cardboard substrate. The beads were then manually contacted with another cardboard substrate for the listed cure times (listed in Table 2). The substrate was then separated manually and then fiber tear was measured by examining the% area of the adhesive layer covered with fibers. The value of fiber tear (% fiber tear) correlates directly with the strength of the adhesive.

  Non-foamed Comparative Example A had a cure time of 3 seconds and 100% fiber tear, but as the foam content in the adhesive increased (increase in percent density reduction), longer cure times and A smaller% fiber tear was produced. Moreover, the cure time and% fiber tear values did not match the same% density reduction, application temperature and even bead weight of Comparative Example C. Examples with a block copolymer having a cure time of at least 3 seconds had an increased% fiber tear value over the comparative example without the block copolymer.

  Thermal stress is defined as the temperature at which a stressed adhesive layer breaks. In the examples after thermal stress, heat resistance was measured using the ability of hot melt to withstand high temperatures under cleavage force (also referred to herein as cleavage thermal stress). Cleavage heat stress was measured using the same protocol described in WO2009 / 1100414. The heat resistance of the sample was measured using the cleavage temperature. Values are listed in Table 3. The recorded cleavage temperature reflects the temperature at which the adhesive softens and the two substrate plates peel from each other. At least four samples were tested. The average cleavage temperature values are listed in Table 3. Density was reduced by mechanically stirring the sample to the percent density reduction shown in Table 3.

  The cleavage temperature for non-foamed Comparative Example A was 63 ° C., but was reduced below 55 ° C. by decreasing the density. As shown in Table 3, the examples using block copolymers maintained heat resistant temperatures in excess of 55 ° C. even when applied at a 30% reduced density. Foamed adhesives using block copolymers provide higher heat resistance than foamed comparative adhesives that do not use block copolymers.

  The thermal stress of Comparative Example E and Example 2 was measured. 2.5 g of azodicarbonamide was added to 100 g of the sample adhesive in Table 4 and blended until uniform and applied at the indicated application temperature. Two 2 ″ × 6 ″ (having a width of 2 ″) corrugated board having a circular groove on the 2 ″ side were prepared. The adhesive was applied to 2 "x 2" of the first corrugated board, and the second board was placed so that 2 "x 2" overlapped. The resulting plate has a 2 "overlap and a 4" single plate on each side. A weight of 200 g was uniformly applied to the overlapped portion at room temperature for 24 hours. After 24 hours, one side of the 4 "board is clamped and a weight of 200 g is applied to the end of the other side of the 4" board and the entire apparatus is placed in the temperature listed in Table 4. It was. Three tests were performed for each temperature to determine whether it passed at that temperature. During the 24 hour test, at the listed temperatures, a weight of 200 g was applied to one end of the plate and the device remained intact without delamination and was considered acceptable.

  As shown in Table 4, the adhesive using the block copolymer (Example 2) had a higher thermal stress value than the adhesive not using the block copolymer (Comparative Example E). The use of alternating blocks of rigid and elastic segments is an essential part of the foamable hot melt adhesive. Heat resistance cannot be imparted by utilizing a high molecular weight, low melt index polymer that does not have alternating blocks of rigid and elastic segments in the foamed adhesive.

  The percent adhesive values for the adhesives are listed in Table 5. Adhesive beads having a diameter of about 3-4 mm were applied to kraft liner paper substrates at the densities and application temperatures listed in Table 5. The article was then stored for 24 hours at the listed storage temperature prior to testing. The percent adhesion was measured by manually peeling the two substrates and the percent of the substrate with fibers was investigated. 100% adhesion indicates that the substrate was completely covered with fibers.

  As demonstrated in Table 5, lower percent adhesion was obtained when the comparative example was foamed. In addition, the percent adhesion values for the foamed examples are similar to those examples that do not have any density reduction at room temperature storage conditions. In addition, Example 3 had similar adhesion values at 0 ° C. even when the density reduction was 50-60%.

  Adhesives using block copolymers have a higher proportion of foam that is taller over longer periods of time than adhesives that do not use block copolymers. Comparative Example D and Example 4 were similarly foamed at 350 ° F. and the height of the foamed adhesive was measured over time. As shown in FIG. 3, Example 4 had a much higher peak foam than Comparative Example D without the block copolymer, and the foam remained in the adhesive longer.

  Foamed adhesives using block copolymers have a higher modulus at higher temperatures than adhesives without block copolymers. As shown in FIG. 1, the modulus (G ′) of Example 2 is higher than an ethylene-vinyl acetate adhesive (TECHNOMELT® 8875 adhesive, Henkel Corporation) that does not use a block copolymer.

  The same adhesive was tested under time sweep conditions and the modulus was measured against time. As demonstrated in FIG. 2, the tan δ curve of Example 2 has a value of 1. This is a transition value between liquid and solid, indicating the gel-like properties of the adhesive using the block copolymer.

  It will be apparent to those skilled in the art that many modifications and variations of the present invention can be made without departing from the spirit and scope of the invention. The specific embodiments described herein are presented by way of illustration only and the present invention is defined by the appended claims and the full scope of equivalents to which such claims are entitled. It shall be limited only by.

Claims (11)

For the total weight of the foamable adhesive composition 100 wt%,
(A) and 90 or, et al. 99.9 wt% of the hot-melt adhesive,
(B) of 0.1 or et 10 wt%, optionally a block copolymer and (c) containing alternating blocks of rigid and elastic segment, including foam and 0.05 or al 10 wt% of the foam cell forming agent a sexual adhesive composition, wherein the foam during the foaming adhesive composition, bubbles in the foamed adhesive has a volume percent of 20 or et 80 V / V%,
Block copolymers over (b) comprises a 5 g / 10 min or more melt index is measured according to A STM D1238, the olefin block copolymer having a DSC melting point in excess of 100 ° C.,
The hot melt adhesive (a) does not include the block copolymer (b).
Foamable adhesive composition.   The foamable adhesive composition of claim 1, wherein the hot melt adhesive comprises a polymer and optionally a wax, tackifier, plasticizer and additives. It said polymer has a crystallinity range of 5% to 60%, the foaming adhesive composition according to claim 2.   4. The polymer of claim 2 or 3, wherein the polymer is selected from the group consisting of amorphous alpha polyolefins, crystalline polyolefins, ethylene vinyl acetate, ethylene butyl acrylate, propylene-hexene copolymers, ethylene-propylene copolymers, and mixtures thereof. The foamable adhesive composition described. The foamable adhesive composition according to any one of claims 1 to 4, wherein the bubbles are generated using a gas, a foam cell forming agent or a plurality of microspheres.   The foaming cell forming agent is azodicarbonamide, oxybis (benzenesulfonylhydrazide), toluenesulfonylhydrazide, diphenylsulfone-3,3′-disulfohydrazide, trihydrazinotriazine, p-toluenesulfonylsemicarbazide, 5-phenyltetrazole, The foamable adhesive composition according to any one of claims 1 to 5, which is selected from the group consisting of isatoic anhydride, sodium hydrogen carbonate, citric acid and mixtures thereof.   An article comprising the foamed adhesive according to any one of claims 1-6. (A) preparing a foamable adhesive composition comprising the hot melt adhesive and the block copolymer;
(B) heating the foamable adhesive composition to a molten state;
(C) mechanically mixing a gas into the molten foamable adhesive composition to produce bubbles in the matrix;
(D) applying the foamed adhesive composition to a substrate, and foaming the foamable adhesive composition according to claim 1. (A) preparing a foamable adhesive composition comprising the hot melt adhesive, the block copolymer, and a foamed cell forming agent;
(B) heating the foamable adhesive composition to T1,
(C) heating the foamable adhesive composition to T2, wherein the foamed cell forming agent is activated at a temperature above T1, thereby foaming the foamable adhesive;
(D) applying a foamed adhesive composition to a substrate, wherein T2 is higher than T1,
The foam cell forming agent is selected from the group consisting of azodicarbonamide, oxybis (benzenesulfonyl hydrazide), toluenesulfonyl hydrazide, 5-phenyltetrazole, sodium bicarbonate, citric acid, acrylic copolymer and mixtures thereof. A method for foaming the foamable adhesive composition described in 1. (A) preparing a foamable adhesive composition comprising the hot melt adhesive, the block copolymer, and a plurality of expandable microspheres;
(B) heating the foamable adhesive composition to T2, wherein the expandable microspheres are activated at a temperature above T1, thereby foaming the foamable adhesive;
(C) applying the adhesive having expanded microspheres to a substrate, wherein T2 is higher than T1, and the adhesive includes essentially zero expansion microspheres at T1. A method for foaming a foamable adhesive composition. 7. The foamable adhesive composition according to any one of claims 2 to 6, wherein the weight ratio of polymer to block copolymer in the hot melt adhesive is in the range of 20: 1 to 2: 1.

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